Wizards of the Coast - the stewards of this indie game called Magic: The Gathering - have finally decided to release a modern, online-only iteration of their collectible card combat game to complete with the likes of Hearthstone and... Gwent? But yeah... mainly Hearthstone. Think of it as a hybrid of Duels of the Planeswalkers and Magic Online with an eye towards accessibility and being spectator-friendly.
You can sign up for the Closed Beta now on the official Magic: The Gathering Arena website.
I have actually started to play some matches this since they did their first beta account wipe. Your beta account now will come with ten dual-colour starter decks and a smattering of booster packs across all of the current Standard format sets. I had found a bit of a content/features road map but lost it for the moment. I seem to remember they plan supporting Commander in Arena which is pretty nuts.
For now you can check out the M:TG Arena FAQ.
I am shaking off my horrid M:TG rust as well as grappling with the almost-but-not-quite-Duels-like UI being used in Arena. So I am getting crushed a lot but the game is very stable, albeit feature-lite, the matchmaking very speedy and the fun factor extremely high.